[perf] Use sync.Once to simplify loadTemplates calling.
[perf] Use sync.Once to simplify loadTemplates calling.

Change-Id: I2f32465aa619099256fa2353f6cccb47af8ab604
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/315280
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot